Repentance is recognizing reality
-from Bruce Charlton (paraphrased)
One thing that quote means (not the only thing) is this: the reality is that sin is really bad. Sinful, in fact. Not least among the ways Christ made repentance possible through the atonement is simply by showing in his person how serious sin is. Sin required the Son of God to suffer. The human character is mostly incapable of taking a transgression seriously if it can simply be waved off.